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Physics Nuclear Experiment

nucl-ex Watch Nuclear Experiment

Wednesday 5 August

Nuclear Experiment · Cross-listed from nucl-th

TITAN mass measurements of neutron-rich Cs, Ba and r-process lanthanide abundances

T.-H. Yeh, J.D. Cardona, Y. Wang et al. (+26 more)

We present measurements for the masses of five neutron-rich isotopes, $^{149-151}$Cs and $^{151, 152}$Ba, probed for the first time by TITAN at TRIUMF with time-of-flight measurement techniques. We propagate these masses to the nuclear reaction and decay data required for the simulation of the rapid neutron capture process (r-process) nucleosynthesis in neutron star mergers. We show that these neutron-rich masses affect the abundance predictions near mass number $A\sim148-152$ corresponding to lanthanide element abundances at $Z=60,\,62$ and $63$. We demonstrate that these new TITAN masses smooth out the odd-even effect in isotopic abundance predictions near $A\sim150$ in both fission cycling astrophysical conditions and conditions that do not reach actinides. We further show that these new masses adjust how fission fragments settle into place when forming the final abundances, and consider the effect on comparisons with stellar abundance ratios such as [Ag/Eu], [Sm/Eu], and [Nd/Eu].
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All authors T.-H. Yeh, J.D. Cardona, Y. Wang, J. Ash, B. Ashrafkhani, I. Belosovic, J. Bergmann, E. Dunling, L. Egoriti, G. Gelinas, G. Gwinner, Z. Hockenbery, C. Izzo, A. Jacobs, S. Kakkar, B. Kootte, E. M. Lykiardopoulou, T. Murbock, A. Mollaebrahimi, A. Ridley, S. F. Paul, W. S. Porter, M. P. Reiter, J. Ringuette, R. Simpson, C. Walls, M. R. Mumpower, N. Vassh, A.A. Kwiatkowski

Nuclear Experiment

ePIC Early Science Report

D. Abbott, N. Abdelrahman, S. Abhijit et al. (+796 more)

This Early Science Report from the ePIC Collaboration outlines the compelling physics program achievable during the first years of operation of the Electron-Ion Collider (EIC), prior to the establishment of the full design luminosity and energy range. The analyses are based on realistic early-running beam configurations and detailed Geant4 ePIC detector simulations, hit digitization and data reconstruction. The projected studies from the physics working groups of ePIC span inclusive, semi-inclusive, exclusive, diffractive and tagging, as well as jet and heavy flavor measurements in both electron-proton and electron-ion collisions. Even before the collider reaches its full design performance, these measurements will constrain parton distribution functions in nucleons and nuclei, access transverse-momentum-dependent and spin-dependent observables, probe gluon dynamics in nuclei, and initiate a program of imaging of quarks and gluons. Each measurement is directly connected to the core science pillars of the EIC, identified in the 2018 report by the National Academy of Sciences: understanding the origin of the nucleon mass, unraveling the spin structure of the nucleon, and exploring the emergent properties of dense gluonic matter. The results presented here provide examples that demonstrate that the early years of EIC running with ePIC will deliver novel world-leading insights into Quantum Chromodynamics. In addition, the early science program will establish measurement and analysis methodologies that will pave the way to the subsequent full EIC physics program.
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All authors D. Abbott, N. Abdelrahman, S. Abhijit, I. Abualrob, R. B. Achari, J. Adam, L. Adamczyk, K. Adkins, A. Affolder, K. Agarwal, J. Agarwala, N. Agrawal, C. A. Aidala, W. Akers, A. Al-bataineh, S. N. Alam, M. Alekseev, P. R. Altieri, J.-S. Alvarado Gallenao, S. B. L. Amar, R. Ammendola, I. Amos Cali, G. An, D. Anderson, E. Anderssen, V. Andrieux, G. Andronico, P. Antonioli, N. Apadula, D. Arkhipkin, W. Armstrong, M. Arratia, S. Arrigo, J. Arrington, M. Asai, A. Asaturyan, E.-C. Aschenauer, C. Ayerbe Gayoso, B. Azmoun, J. Bae, Y. Bae, X. Bai, V. Bailey, F. Barbosa, F. Barile, K. Barish, M. Bashkanov, S. Bathe, M. Battaglieri, A. Baty, A. Bazilevsky, T. D. Beattie, B. Beauchamp, Y. Bedfer, N. K. Behera, F. Bellini, R. Bellwied, H. Ben Hannan, M. Benettoni, M. Benoit, V. Berdnikov, J. Bernauer, H. Bervas, R. Besuner, J. Bettane, R. Bhadauriya, H. Bhatt, V. Bhopatkar, S. Bhosale, A. Biagioni, J. Bielcikova, J. Bielčík, Z. Biro, G. Boca, F. Bock, J. Bok, M. Bondi, A. Bonenfant, C. Bonini, M. Borri, F. Bossù, F. Bouyjou, O. Brand-Foissac, D. Brandenburg, N. Brei, A. Bressan, T. Britton, G. E. Bruno, M. Buckland, A. Buckley, L. Bucuru, E. Buron, A. Bylinkin, D. Cacace, H. Caines, A. Calivà, M. T. Camerlingo, P. Campero Rojas, A. Camsonne, M. Capua, F. Capuani, T. Carmarda, E. Casalotti, J. Ceska, I. Chakaberia, J. Chan, W.-C. Chang, M. Chartier, P. Chatagnon, C. Chatterjee, V. Chaumat, K.-F. Chen, Z. Chen, K.-Y. Cheng, Y. Cheng, S. Chevobbe, A. Cheyne, C. Chiarini, A. Chisari, S. Choi, P. Christoph, X. Chu, J. Chwastowski, A. Ciardiello, S. Ciarlantini, A. Cimini, E. Cisbani, Z. Citron, E. Cline, I. Cloët, D. Colella, M. Connors, M. Contalbrigo, G. Contin, S. Corey, R. Corliss, T. Cornet, F. Cossio, S. Costanza, J. Crafts, D. Cristancho, R. Cruz-Torres, A. D'Angelo, A. Dabat-Blondeau, E. Dahle, S. Dalla Torre, M. Daradkeh, S. Das, A. P. Dash, J. Datta, P. Datta, K. Davies, R. Dawson, A. De Caro, D. De Gruttola, S. De Pasquale, W. Deconinck, M. Defurne, Y. Degerli, C. Delafosse, A. Delbart, F. Delcarro, G. Dellacasa, M. Demarteau, Z. S. Demiroglu, G. W. Deptuch, A. Deshpande, D. Di Bari, B. Di Ruzza, R. Di Salvo, M. Diefenthaler, C. M. S. Divincenzo, X. Dong, B. Dongwi, V. Doomra, N. Doshita, A. Drees, R. Dupre, D. Dutta, R. Dzhygadlo, A. El Ouardi, L. El Fassi, D. Elia, B. Eng, R. Ent, Y. Eo, R. Esha, A. Eslinger, A. Evdokimov, O. Evdokimov, O. Eyser, V. Fadeyev, D. Falchieri, W. Fan, C. Fanelli, A. Fantini, F. Farrokhi, R. Fatemi, S. Fazio, S. Fegan, M. Finger, M. Finger, F. Flor, L. Flores, C. Flouzat, E. Fountain, B. Fraisse, A. Francisco, J. Frantz, S. Franzese, O. Frezza, N. Funicello, S. Furletov, Y. Furletova, C. Gal, H. Gao, M. Garbini, S. Gardner, P. Garg, D. Gaskell, V. Gaur, S. Geminiani, M. Gericke, F. Geurts, O. Gevin, T. Ghosh, P. Ghoshal, A. Gibson, I. Gildea, R. Gilman, D. Giordano, A. Giri, J. Giroux, P. Giubilato, D. I. Glazier, E. Glimos, J. Glover, K. Gnanvo, Y. Go, C. Goblin, L. Godfrey, L. Gonella, S. Gopinath, D. Gorni, M. Gouighri, S. Gramigna, K. Gray, S. V. Greene, M. Grosse Perdekamp, W. Gu, F. Guilloux, T. Gunji, J. Gupta, C. Gwenlan, T. Hachiya, E. Hagen, J. Haggerty, T. Hague, W. Ham, A. Hamed, R. Hamilton, X. Han, O. Hartbrich, M. C. Harvey, H. Hashamipour, S. Hassan, M. Hattawy, L. Havener, X. He, T. Hellstern, W. Helsby, T. Hemmick, O. Hen, S. Henry, D. Higinbotham, A. Hill, M. Hoballah, A. Hoghmrtsyan, M. Hohlmann, B. Hong, Y. Hong, T. Horn, D. Hornidge, I. Hossain, T. Hotta, C.-Y. Hsieh, Y. Hu, H. Z. Huang, J. Huang, J. Huang, S. Huang, G. Huber, A. Huddart, T. Huffman, P. Hurck, T. Hwang, C. Hyde, S. Iain, P. Iapozzuto, A. Illari, M. Inaba, G. M. Innocenti, A. Iqbal, D. G. Ireland, L. Isenhower, B. Jacak, N. Jacazio, M. Jadhav, S. Jain, H. Jang, S. Jang, O. Javakhishvili, J. Jaya, F. Jeanneau, A. Jentsch, Y. Jeong, T. Jeske, O. T. Jevons, S. Ji, J. Jia, H. Jiang, N. Jindal, H.-S. Jo, P. Jones, K. Joo, S. Joosten, A. Jung, O. Ka, G. Kainth, J. Kalani, N. Kalantarians, G. Kalicy, D. Kalinkin, M. Kaneta, K. Kauder, R. Kaundal, K. Kawade, S. Kay, M. Kebbiri, M. Kesler, A. Khanov, H. Khindri, A. Khuntia, Y. Khyzhniak, C. Kierans, A. Kim, B. Kim, B. Kim, C. Kim, E.-J. Kim, E. Kim, G. Kim, J. Kim, M. Kim, M. Kim, S. H. Kim, J. Kiryluk, A. Kiselev, J. Klay, S. Klein, H. Klest, V. Klimenko, N. Kobayashi, R. Koka, O. Korchak, I. Korover, L. Kosarzewski, A. Kostina, I. Krehbiel, A. Krieger, F. Krizek, T. Kumaoka, A. Kumar, K. Kumar, L. Kumar, R. Kumar, S. Kumar, M. Kumari, R. Kunnawalkam Elayavalli, C.-M. Kuo, T. Kutz, Y. Kwon, B.-Y. Ky, P. La Rocca, M. Labiche, R. Lacey, J. Lajoie, J. Lalic, K. Lalwani, E. Lancon, J. Landgraf, L. Lanza, R. Lassiter, D. Lattuada, J. Lauret, A. Laviron, O. Le Dortz, C. Le Gaillard, Y. Le Roux, C. Lee, H. Lee, H. Lee, J. Lee, J.-H. Lee, K. Lee, S. Lee, S. Lee, S.-J. Lee, Y.-J. Lee, S. Levorato, N. Lewis, S. Li, W. Li, W. Li, X. Li, B. Liang-Gilman, H. Lim, S. Lim, P.-J. Lin, W. Lin, M. Lisa, A. Liu, J. Liu, M. Liu, M. Liu, K. Livingston, T. Ljubicic, W. Llope, F. Lo Cicero, O. Lomický, A. Lonardo, E. Long, L. Long, R. Longo, S. Longo, R.-S. Lu, A. Lumanog, R. Ma, P. Maj, J. Mammei, F. Mammoliti, G. Mandaglio, S. Mandal, I. Mandjavidze, V. Manzari, S. Maple, D. Marchand, C. Markert, A. Martin, M. Martinelli, H. Marukyan, A. Mastroserio, G. Matousek, K. Matsutani, S. Mattiazzo, J. Maxwell, S. Mazza, B. McKinnon, A. S. Menon, J. Metcalfe, Z.-E. Meziani, A. Migayron, R. Milner, R. Milton, N. Minafra, C. Mingioni, Y. Miyachi, A. Mkrtchyan, H. Mkrtchyan, E. F. Molina Cardenas, M. K. A. Mondal, R. Montgomery, I. Mooney, B. Moreno, D. Morrison, S. Mouslih, A. Movsisyan, C. Munoz Camacho, S. Muraoka, M. Murray, T. Nagorna, C. J. Naim, A. Nambrath, S. Nanda, E. Nappi, V. Narendran, A. Natochii, V. S. Nattoja, C. Nattrass, H. Nayak, G. Nebin, D. Neff, M. Nenni, P. Newman, D. Neyret, M. Nguyen, N. Nicassio, S. Niccolai, G. Nigmatkulov, F. Noferini, P. Nord, J. Norman, R. Nothnagel, F. Noto, R. Nouicer, N. Novitzky, C. Nunez, J. Nystrand, S. Obratsov, L. Occhiuto, A. Ogawa, C. Oh, S. Oh, O. Olokunboyo, J. Osborn, M. Osipenko, S. Ota, J. Ott, G. Ottino, K. Oyama, E. O'Brien, B. S. Page, S. Pal, A. Paladino, P. Palni, A. Pandav, V. Pant, A. Panta, C. Pantouvakis, D. Panzieri, Z. Papandreou, S. Park, C. Pastore, V. K. Patel, S. Paul, S. Paul, C. Pecar, C. Peng, G. Penman, R. Perrino, P. Perticaroli, N. Pilleux, C. Pinkenburg, R. Pisani, S. Plavully, L. Polizzi, I. Ponce, L. Pontisso, M. Posik, M. Potekhin, E. Pottebaum, S. Prabhakar, R. Prabir, L. Preet, R. Preghenella, S. Priens, E. Prifti, M. Priyadarshini, I. Prochazka, T. Protzman, A. Prozorov, F. Prunes, M. Przybycien, P. Pujahari, P. Purohit, M. Purschke, B. Quni, S. Radhankrishnan, M. Radici, A. Rafaat, S. Rafael-Polcher, S. Rahman, R. Rajput-Ghoshal, A. Ramalingam, S. Rana, E. Rao, A. Rathi, F. Rathmann, A. Rathore, K. Read, P. Rebesan, R. Reed, B. Rehman, P. Reimer, G. Reis Garcia, J. S. Renck, S. Rescia, R. Ricci, J. Richards, C. Riedl, A. Riggio, L. Rignanese, M. Ripani, C. Ripoli, F. Rizatdinova, D. Rizk, J. Roche, G. Roland, D. Romanov, M. Rosati, C. Rossi, F. Rossi, E. Rovati, L. Ruan, N. Rubini, M. Ruspa, D. Ruth, J. Ryu, S.-Y. Ryu, F. Sabatié, R. Sadek, H. Sadrozinski, N. Saha, T. Sakaguchi, S. Salur, D. Samuel, P. Sanethavong, N. Santiesteban, A. Saputi, A. Sarkar, M. Sarsour, J. Schambach, B. Schmookler, B. Schumm, C. Schwarz, J. Schwiening, A. Seiden, R. Seidl, B. Seitz, H. Seong, L. Serin, Y. Shabaan, N. Shah, M. Shahid, P. Shanmuganathan, A. Sharma, D. Sharma, R. Sharma, A. Shatat, A. I. Sheikh, T.-A. Shibata, K. Shigaki, G. Shildt, T. Shin, S. Shiraskar, J. Shirk, J.-G. Shiu, N. Shouryasankar, E. Shulga, E. Sichtermann, E. Sidoretti, J. Silber, F. Simula, A. Singh, B. K. Singh, G. Singh, J. Singh, K. Slifer, N. Smirnov, A. Smith, J. Smith, K. Smith, D. Sokhan, G. Sommer, T. Song, R. Souvik, N. Speece-Moyer, F. Spizzo, M. Spreafico, N. St John, M. Stefaniak, P. Steinberg, J. Stevens, S. Stoll, E. Sun, K. Suresh, B. Surrow, M. C. Sutera, K. Sutowski, T. Sykora, H. Szumila-Vance, V. Tadevosyan, T. Takahshi, C. K. Tam, A. Tamis, U. Tamponi, X. Tan, D. Tapia Takaki, S. Tarafdar, E. Tassi, Y. Tayalati, L. Teodorescu, C. Terrevoli, F. Tessarotto, A. Teymurazyan, M. Thakur, D. Thomas, F. Thomson, A. Timmins, S. Titus, T. Toll, L. Tomasek, A.-S. Torrento, P. Tribedy, B. A. Trzeciak, O. Tsai, C. S. Tse, Z. Tu, R. Turrisi, C. Tuvé, B. Ujvári, T. Ullrich, G. M. Urciuoli, S. Vallarino, N. Valle, C. Van Hulse, M. Vandenbroucke, J. Vanek, Z. Varga, N. Vasim, J. Vasquez, S. Vasquez, J. Velkovska, G. Verde, S. Vetter, P. Vicini, G. Viehhauser, A. Vijay, A. Vijayakumar, D. Violette, T. Virgili, G. Volpe, A. Vossen, E. Voutier, F. Wang, G. Wang, P.-K. Wang, Y.-T. Wang, R. Wastie, J. Watkins, I. J. Watson, D. P. Watts, S. Welch, T. Wenaus, F. Wilson, R. Wimmer, S. Wissink, H. Witte, M. Wood, C. Woody, Y.-H. Xiao, J. Xie, W. Xie, Z. Xu, Z. Xu, Z. Xue, S. Yang, S. Yang, Y. Yang, S. Yano, Z. Ye, Z. Ye, Z. Ye, E. Yeats, K. Yip, K. Yongsun, H. Yoo, I. Yoon, D. Young, C. Yuen Tsang, N. Zachariou, W. Zha, S. Zhang, W. Zhang, Y. Zhang, Y. Zhang, Z. Zhang, Z. Zhang, Y. Zhao, Z. Zhao, V. Zhezer, B. Zihlmann, C. Zorn, M. Zurek, J. de Melo, D. de Souza Lemos, A. Accardi, I. Borsa, M. Cerutti, C. Cocuzza, J. Jiménez-López, K. Kumericki, R. Martinez, L. Rossi, P. Sznajder, A. Vladimirov, K. Wichmann, S. Yadav, P. Zurita

Nuclear Experiment · Cross-listed from hep-ph

Photon-nucleon entanglement in Compton scattering at low and high energies

Yoshitaka Hatta and Víctor Martínez-Fernández

We study spin-spin entanglement in the final state photon-nucleon system in Compton scattering, both at low energy below the pion threshold and at high energy in perturbative QCD to next-to-leading order. We first establish a no-go theorem showing that, for any spin-$\frac{1}{2}$ target, entanglement cannot be generated in unpolarized Compton scattering if the scattering amplitudes are real. We then consider polarized Compton scattering off the electron, the proton and the neutron. At low energy, we uncover a rich variety of maximally entangled Bell states and their unitary equivalents realized across different regions of the kinematic plane. Interestingly, the proton and neutron targets exhibit distinct patterns of entanglement. In the neutron case, the electric and magnetic polarizabilities dramatically influence the pattern and even the existence of entanglement. This suggests that entanglement can serve as a novel tool for investigating the detailed electromagnetic properties of the nucleons.
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Nuclear Experiment

First Results on Nucleon Resonance Electroexcitation Amplitudes from $ep \to e'\pi^+\pi^-p'$ Cross Sections at $W$ from $1.56-1.76$ GeV and $Q^2$ from $2.0-5.0$ GeV$^2$

V.I.Mokeev, P.Achenbach, V.D.Burkert et al. (+6 more)

The first results on the electroexcitation amplitudes or the $\gamma_vpN^*$ electrocouplings for nucleon resonances ($N^*$s) in the third resonance region are presented. They were obtained from $\pi^+\pi^-p$ electroproduction differential cross sections measured with the CLAS detector and analyzed using the Jefferson Lab-Moscow State University (JM) reaction model. The analysis covers the invariant mass range of the final-state hadrons $W$ from 1.56 to 1.76~GeV and virtual photon four-momentum squared $Q^2$ from 2.0 to 5.0~GeV$^2$. Consistent results on the electroexcitation amplitudes of the $N(1675)5/2^-$ and $N(1680)5/2^+$ obtained from independent analyses of both $\pi N$ and $\pi^+\pi^-p$ final states, demonstrate the capability of reaction models to extract the $\gamma_v p N^*$ electrocouplings for $N^*$s in the third resonance region. Also, for the first time, the electrocouplings of the $\Delta(1700)3/2^-$ and $N(1720)3/2^+$, which predominantly decay into $\pi\pi N$ final states, have become available for $Q^2 > 2.0$~GeV$^2$. Finally, contributions from a new $N'(1720)3/2^+$ baryon state to the $\pi^+\pi^-p$ differential cross sections have been observed for $Q^2 < 5.0$~GeV$^2$. The new results on resonance electrocouplings in the third resonance region offer new opportunities to explore various aspects of the strong QCD regime responsible for the generation of nucleon excited states, in particular, shedding light on the emergence of hadron mass in connection with dynamical chiral symmetry breaking.
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All authors V.I.Mokeev, P.Achenbach, V.D.Burkert, D.S.Carman, R.W.Gothe, E.L.Isupov, K.Joo, K.Neupane, Y.Wunderlich

Nuclear Experiment · Cross-listed from astro-ph.HE

Bayesian Inference of fine-features of dense matter EOS from future high-precision data of neutron star radii

Bao-An Li, Xavier Grundler, Wen-Jie Xie et al. (+1 more)

Future high-precision X-ray and gravitational wave observatories are expected to measure the radii of neutron stars (NSs) with an accuracy better than about 0.1 km. However, it remains unclear what particular aspects of the Equation of State (EOS) and to what precision they will be better constrained. Within a Bayesian framework using a meta-model EOS and mock high-precision NS data, the posterior probability distribution functions (PDFs) of NS matter EOS parameters for both hadronic and quark phases and the transition between them were recently studied. We report here a few highlights of these studies.
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All authors Bao-An Li, Xavier Grundler, Wen-Jie Xie, Nai-Bo Zhang

Nuclear Experiment

News on charged and neutral hadron production from NA61/SHINE

Yuliia Balkova and Maciej P. Lewicki

Strangeness production in high-energy hadronic and nuclear collisions remains a central topic in the study of strongly interacting matter under extreme conditions. The data collected by the NA61/SHINE experiment at the CERN SPS allow for a comprehensive scan of hadron production across various collision energies and system sizes. This article focuses on new results on charged and neutral hadron production in central collisions of medium-sized nuclei, such as Ar+Sc and Xe+La, in the SPS energy range. First, the energy and system-size dependence of the $K^+/\pi^+$ ratio is discussed, confirming the “horn” structure in central Pb+Pb collisions and its absence in smaller systems. Furthermore, the inverse slope parameter $T$ of kaon transverse mass (transverse momentum) spectra is analyzed, showing that intermediate-size systems reach values comparable to those observed in central Pb+Pb collisions. Second, normalized proton rapidity spectra $(\text{d}n/\text{d}y)/\langle W \rangle$ in central Be+Be, Ar+Sc, and Pb+Pb collisions are presented, demonstrating energy-dependent baryon transport as a function of system size. Building on this baseline, $\Lambda$ hyperon production in central Ar+Sc collisions is explored across SPS energies, where rapidity spectra, mean multiplicities ($\langle \Lambda \rangle$), and ratios to pions are compared with model predictions and existing data. Finally, an anomalous excess of charged over neutral kaons ($R_K > 1$) in central Ar+Sc collisions is reported, highlighting a potential unexpectedly large violation of isospin symmetry.
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Nuclear Experiment · Cross-listed from astro-ph.HE

Type I X-Ray Burst Models With Rotation

David Martin and Jordi Jose

Type I X-ray bursts are powered by unstable thermonuclear burning on the surface of accreting neutron stars in close binary systems. These brief X-ray flashes, with light curves featuring rise times of $1-10$ s, durations of $10-100$ s, and recurrence periods of hours to days, represent the most frequent stellar explosions in our Galaxy. With typical energies of $\sim 10^{39}-10^{40}$ erg, they rank among the most powerful astrophysical transients after supernovae and classical novae. To date, roughly 120 bursting X-ray binaries have been identified in the Milky Way. Several studies have been conducted to characterize the dynamics of these events, with emphasis on reproducing the observed recurrence periods and light curve shapes. In this paper we show, for the first time, that rotation is a key factor shaping the properties of Type I X-ray bursts in rapidly spinning systems. The inclusion of centrifugal forces, together with a suite of rotationally-induced mixing mechanisms, such as meridional circulation and shear-induced turbulent diffusion, reduce surface gravity, shortening the recurrence times and lowering burst energies. Rotation also modifies the extent of the nuclear activity during these events and affects the morphology of their light curves, which are distinctly broader for rapidly rotating neutron stars.
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Nuclear Experiment

Directed Flow of Protons and Deuterons in Xe+Cs(I) Collisions: Preliminary BM@N Data and THESEUS Modeling

M. E. Kozhevnikova, M. V. Mamaev, I. A. Zhavoronkova et al. (+2 more)

Preliminary BM@N results on the directed flow ($v_1$) of protons and deuterons in Xe+Cs(I) collisions at 3.8$A$ GeV are presented for the 10-40% centrality interval. The measured rapidity dependence of $v_1$ is compared with calculations from the THESEUS event generator, where deuterons are produced thermodynamically on an equal basis with hadrons using a late freeze-out scenario. While THESEUS well describes the proton $v_1$ data, it shows a slight but systematic overestimation of the deuteron flow at low and intermediate rapidities. This comparison tests both the collective dynamics of baryon-rich matter and the thermodynamic mechanism of light-nucleus formation at Nuclotron energies.
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All authors M. E. Kozhevnikova, M. V. Mamaev, I. A. Zhavoronkova, A. V. Taranenko, Yu. B. Ivanov

Nuclear Experiment · Cross-listed from quant-ph

State-resolved quantum-information fingerprints of partial dynamical symmetry in the interacting boson model

Dhritimalya Roy

Partial dynamical symmetry (PDS) is an algebraic structure in which a symmetry is neither exact nor fully broken: a subset of eigenstates keeps good quantum numbers and stays solvable while the rest mix. It is currently identified from spectroscopy. We ask whether it also leaves a purely structural mark in the eigenstates, and find, for the $sd$-IBM Hamiltonians studied here, that it does, though not in the magnitude of entanglement. The diagnostic is the variance of a symmetry Casimir, the label variance $\Var\,\C[G]$, which shares its zero with a block-coherence entropy and a block impurity: all three vanish when a state occupies a single Casimir sector, a single irreducible representation once conjugate representations are resolved by the cubic Casimir. Resolved state by state, the variance is numerically zero on the symmetry-selected subset and large on the mixed states, isolating the PDS states from the wavefunctions alone; the separation does not close as the boson number grows and persists at Leviatan's first- and second-order critical points, whereas the magnitude of bipartite $s|d$ entanglement does not separate the two families. We anchor the analysis in $^{168}$Er, reproducing Leviatan's fitted $\su3$ admixtures and his Hamiltonian-parameter-independent $\gamma\!\to\! g$ $B(E2)$ ratios. The diagnostic also has an exact dynamical form, a Casimir Loschmidt echo rigid on the symmetry-pure states, and we demonstrate its readout on an IBM superconducting processor at $N=3$, where a single solvable/mixed exemplar reproduces the predicted pattern within finite-shot uncertainties.
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Tuesday 4 August

Nuclear Experiment · Cross-listed from physics.ins-det

Optical characterization and ionizing-radiation response of the BCF-20XL scintillating-wavelength-shifting fiber

W. Bae, L. Baker, K. Chen et al. (+12 more)

We report optical characterization and ionizing-radiation measurements of the scintillating-wavelength-shifting (Sci-WLS) fiber BCF-20XL from Luxium Solutions. Attenuation lengths were obtained from transmitted emission spectra using a 3.0 m fiber with a spectrophotometer and described with a two-component attenuation model, yielding a long attenuation length of 6.70 m and a short attenuation length of 0.16 m. The spectral measurements also reveal wavelength-dependent attenuation, with the long component increasing with wavelength and the short component becoming less significant at longer wavelengths. The scintillation response was also characterized under radioactive alpha, beta, and gamma irradiation using SiPM-based readout, providing a benchmark measurement of the light output from BCF-20XL.
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All authors W. Bae, L. Baker, K. Chen, J. Cho, K. Lang, C. Lee, E. Liang, C. Mathurin, C. Murthy, D. Myers, S. Nguyen, D. Phan, M. Proga, M. Zalikha, J. Zey

Nuclear Experiment · Cross-listed from hep-ph

Direct versus resolved photons in DPS in photoproduction on proton and nuclei

B. Blok and R. Segev

We study the process of double parton scattering (DPS) associated with the photoproduction at a future Electron-Ion collider (EIC) and HERA. We show that in the case of the resolved photon the 1 to 2 processes lead, even at small transverse momenta of the hard processes , to the increase of the DPS by a factor of order 1.6 in the significant part of the phase space, relative to the predictions of the mean field based models . Moreover we study the kinematic region where direct photon contribution is dominant and show it s boundaries for charm and light quark jets. For charmed jets we see that the relevant region is $x_\gamma\ge 0.2-0.4$. This region is even enhanced if we consider the photoproduction on the nuclei.
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Nuclear Experiment

Statistical and non-statistical $\gamma$-decay properties of $^{64}$Zn

A. C. Larsen, M. Guttormsen, T. K. Eriksen et al. (+23 more)

We present a study on the $\gamma$-decay properties of $^{64}$Zn using the Oslo method on $^{64}$Zn($p,p^\prime \gamma$) data combined with $^{64}$Zn$(\gamma,n)$ cross-section measurements at the NewSUBARU facility. With the Oslo method, we have measured the $\gamma$-ray strength function ($\gamma$SF) and the nuclear level density (NLD) below the neutron threshold. We observe that the NLD trend in the quasi-continuum region of $^{64}$Zn is best characterized by a constant-temperature-like model. %with temperature parameter $T_{\rm CT}=1.21(5)$ MeV. Surprisingly, we find that $\gamma$-ray transitions from the quasi-continuum decaying directly to the $0^+$ ground state seem to be strongly hindered with a hindrance factor of $\kappa \approx 0.5$, which could be an indication of non-statistical effects in the ground-state decay due to, e.g., differences in nuclear shapes. For $\gamma$ energies above the neutron separation energy, the NewSUBARU ($\gamma, n$) data set probes a significant part of the giant dipole resonance. Furthermore, we find that the Oslo-method $\gamma$SF shows a rather smooth behavior, with a clear low-energy enhancement (LEE) for $E_{\gamma} < 4$ MeV.
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All authors A. C. Larsen, M. Guttormsen, T. K. Eriksen, G. M. Tveten, H. Utsunomiya, J. K. Dahl, N. Shimizu, T. Ari-izumi, F. L. Bello Garrote, L. T. Bell, M. M. Bjørøen, F. W. Furmyr, D. Gjestvang, A. Görgen, V. W. Ingeberg, K. C. W. Li, E. Lima, M. Markova, E. F. Matthews, A. H. Mjøs, S. Miyamoto, V. Modamio, T. Renstrøm, E. Sahin, S. Siem, M. Wiedeking

Nuclear Experiment · Cross-listed from nucl-th

Finite-spectrum Lorentz integral transform calculation of the $^{4}$He photoabsorption cross section in the no-core shell model

P. Yin, H. T. Zhao, C. Y. Zhai et al. (+11 more)

We develop and validate a finite-spectrum implementation of the Lorentz integral transform (LIT) within the ab initio no-core shell model (NCSM) for calculating the photoabsorption cross section of $^4$He. A large set of $1^-$ eigenstates is explicitly calculated in the NCSM, and the LIT is constructed from their excitation energies and the corresponding $E1$ transition strengths. This finite-spectrum approach is complementary to conventional inhomogeneous-equation and Lanczos-based implementations of the LIT method for photoabsorption cross sections. Using the Daejeon16 interaction, we extract the photoabsorption cross section and examine its stability with respect to the model-space truncation, excitation-energy cutoff, and LIT parameters. The reliability of the finite-spectrum extraction is assessed by comparing the $E1$ polarizability and bremsstrahlung sum rule obtained from the discrete NCSM spectrum with the same quantities obtained by integrating the extracted cross section. The extracted cross section captures the principal features of the available $^4$He photonuclear data in the giant-dipole-resonance region and is consistent, in the low-energy rise and main-peak region, with earlier chiral-interaction NCSM-LIT results obtained from Lanczos-based evaluations, while the present calculation with the Daejeon16 interaction exhibits a more pronounced high-energy shoulder. The present work provides a controlled finite-spectrum NCSM-LIT route from explicitly calculated many-body eigenstates and transition strengths to photoabsorption cross sections.
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All authors P. Yin, H. T. Zhao, C. Y. Zhai, J. P. Vary, H. Li, J. M. Dong, H. J. Ong, X. Zhao, P. J. Fasano, A. M. Shirokov, J. Chen, D. Y. Tao, B. Zhou, C. Ji

Nuclear Experiment · Cross-listed from hep-ph

On the nature of fully-charmed four-quark exotic state $X(6900)$ from its photoproduction off nuclei

E. Ya. Paryev

The possibility to study the nature of fully-charmed tetraquark state $X(6900)$ from its inclusive photoproduction off nuclei near the kinematic threshold is investigated within the collision model based on the nuclear spectral function. The model accounts for $X(6900)$ production in direct photon–nucleon interactions as well as three different scenarios for its internal structure: compact tetraquark, molecule of the two hidden-charm $J/\psi$ and $\psi(3770)$ mesons and the mixture of both of them. We calculate within these scenarios the absolute and relative excitation functions on $^{12}$C and $^{184}$W nuclei at near-threshold photon energies of 30–40 GeV, the absolute momentum differential cross sections and ratios of them for the $X(6900)$ meson production off these target nuclei at laboratory polar angles of 0$^{\circ}$–5$^{\circ}$ and for photon energy of 35 GeV as well as the A-dependences of its transparency ratios at photon energy of 35 GeV. We show that these observables reveal a definite sensitivity to the $X(6900)$ intrinsic structure. Therefore, they might be useful for the determination of this structure from the comparison of them with the experimental data from the future experiments at the upcoming experimental facilities, such as the planned electron-ion colliders in the United States and China.
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Nuclear Experiment

Measurement of forward jet suppression in Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$$ TeV with the ATLAS detector

ATLAS Collaboration

Inclusive jet production is measured with the ATLAS detector at the LHC at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV in Pb+Pb and $pp$ collisions, using data samples corresponding to integrated luminosities of 1.72 nb$^{-1}$ and 255 pb$^{-1}$, respectively. The jet nuclear modification factor, $R_{\mathrm{AA}}$, is reported for anti-$k_t$ jets with radius parameter $R=0.4$ in the forward-rapidity intervals $2.8<|y|<3.2$ and $3.2<|y|<3.6$, probing transverse momenta $p_\mathrm{T}>74$ GeV. The observed $R_{\mathrm{AA}}$ values show a significant suppression of jet yields in Pb+Pb collisions relative to those measured in $pp$ collisions. The suppression increases monotonically from peripheral to central collisions and exhibits a mild jet $p_\mathrm{T}$ dependence. A comparison with previous ATLAS measurements indicates stronger jet suppression in the $2.8<|y|<3.2$ region than in the $|y| < 2.8$ region. In the $3.2<|y|<3.6$ region, the precision of the measurement does not allow a conclusive comparison with the $|y|<2.8$ region. These results constitute the first measurement of inclusive jet suppression at forward rapidity in heavy-ion collisions and provide new constraints on flavor, geometric, and medium-density dependence of parton energy loss.
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Monday 3 August

Nuclear Experiment · Cross-listed from physics.ins-det

Mitigating warp divergence in GPU optical photon Monte Carlo: an order of magnitude speedup with Shader Execution Reordering

Gabor Galgoczi

In high energy, nuclear, and medical physics, optical photon transport Monte Carlo is a frequent bottleneck in detector simulation. GPU ray tracing accelerates photon propagation, but one thread per photon megakernels suffer from SIMT execution divergence when photon lifetimes vary widely. Short-lived photons leave inactive lanes while a few long-lived photons delay warp completion. We evaluate NVIDIA Shader Execution Reordering (SER) in an OptiX based optical photon transport kernel and use it to regroup surviving photons during propagation. In a 14.7 kton liquid argon time projection chamber benchmark with ~61 million photons from a 2.5 GeV electromagnetic shower, SER capable execution reduces propagation kernel cycles by 16.55(23)x and end-to-end optical simulation time, including transfers and initialization, by 14.72(30)x with bit-identical hit output. We decouple the speed-up into a 3.2x contribution from the launch configuration changes introduced when SER is enabled and a further 5.1x from executing the reorder. Profiling identifies active lane recovery as the dominant mechanism, while branch efficiency and memory bandwidth change little. A volume coherent SER hint enables an analytic navigation fast path in bulk argon, adding a further 1.13x wall-time speedup. Utilizing SER resulted in a ~90% reduction in GPU energy per simulated event.
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Nuclear Experiment

Strangeness production in light-ion collisions with ALICE at the LHC

Sara Pucillo for the ALICE Collaboration

Measurements in pp and p–A collisions have revealed that small collision systems exhibit most of the signs traditionally attributed to heavy-ion collisions, such as the smooth increase of the strange hadron yields with the collision multiplicity (strangeness enhancement). A key question is how these effects evolve with system size and whether they can be described within a unified framework. The recently collected oxygen–oxygen (OO) collision data by ALICE at $\sqrt{s}$ = 5.36 TeV provide an unprecedented opportunity to explore an intermediate-size system that naturally bridges the gap between pp and Pb–Pb collisions. In this contribution, we present the first results on the production of (multi-)strange particles as a function of charged-particle multiplicity in OO collisions. This allows us to investigate strangeness enhancement across different system sizes at comparable multiplicities, providing new insights into the mechanisms of strangeness production. The experimental results are compared with model predictions from various Monte Carlo generators.
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Nuclear Experiment

Elliptic flow of $\pi^0$ mesons in Cu$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV and U$+$U at $\sqrt{s_{_{NN}}}=193$ GeV

PHENIX Collaboration: N.J. Abdulameer, U. Acharya, C. Aidala et al. (+380 more)

The second-order azimuthal anisotropy coefficients ($v_2$) of neutral $\pi$ mesons ($\pi^0$) have been measured as a function of the transverse momentum ($p_T$) and centrality of Cu$+$Au collisions at $\sqrt{s_{_{NN}}}=200$~GeV and U$+$U at $\sqrt{s_{_{NN}}}=193$ GeV at the Relativistic Heavy Ion Collider. The analysis used experimental data collected by the PHENIX experiment at midrapidity $|\eta|<0.35$ over a broad $p_T$ range up to $\approx10$~GeV/$c$, and the obtained results are compared with previous PHENIX measurements in Au$+$Au collisions at $\sqrt{s_{_{NN}}}=200$~GeV. In all three collision systems, the $\pi^0$~$v_2$ values follow the scaling with the second-order participant eccentricity and the cube root of the number of participating nucleons ($\varepsilon_2 N_{\rm part}^{1/3}$) up to $\approx4$~GeV/$c$. Furthermore, the behavior of the azimuthal-dependent $\pi^0$ nuclear-modification factors and associated fractional parton-energy losses are evaluated from measured nonzero $v_2$ values of $\pi^0$ at $p_T>5$ GeV/$c$ and found to be approximately the same for similar values of $N_{\rm part}^{1/3}$ in these collision systems. These findings demonstrate that the mechanism of $\pi^0$ $v_2$ generation exhibits a high degree of universality across different initial geometries of heavy-ion collisions.
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All authors PHENIX Collaboration: N.J. Abdulameer, U. Acharya, C. Aidala, N.N. Ajitanand, Y. Akiba, R. Akimoto, J. Alexander, D. Anderson, S. Antsupov, K. Aoki, N. Apadula, H. Asano, E.T. Atomssa, T.C. Awes, B. Azmoun, V. Babintsev, M. Bai, X. Bai, B. Bannier, E. Bannikov, K.N. Barish, S. Bathe, V. Baublis, C. Baumann, S. Baumgart, A. Bazilevsky, M. Beaumier, R. Belmont, A. Berdnikov, Y. Berdnikov, L. Bichon, D. Black, B. Blankenship, D.S. Blau, J.S. Bok, V. Borisov, K. Boyle, M.L. Brooks, J. Bryslawskyj, H. Buesching, V. Bumazhnov, S. Butsyk, S. Campbell, P. Chaitanya, C.-H. Chen, D. Chen, M. Chiu, C.Y. Chi, I.J. Choi, J.B. Choi, S. Choi, P. Christiansen, T. Chujo, V. Cianciolo, B.A. Cole, M. Connors, R. Corliss, N. Cronin, N. Crossette, M. Csanád, T. Csörgő, L. D'Orazio, A. Datta, M.S. Daugherity, G. David, K. Dehmelt, A. Denisov, A. Deshpande, E.J. Desmond, L. Ding, V. Doomra, J.H. Do, O. Drapier, A. Drees, K.A. Drees, J.M. Durham, A. Durum, T. Engelmore, A. Enokizono, R. Esha, K.O. Eyser, B. Fadem, D.E. Fields, M. Finger Jr., M. Finger, D. Firak, D. Fitzgerald, F. Fleuret, S.L. Fokin, J.E. Frantz, A. Franz, A.D. Frawley, Y. Fukao, T. Fusayasu, K. Gainey, C. Gal, P. Garg, A. Garishvili, I. Garishvili, F. Giordano, A. Glenn, X. Gong, M. Gonin, Y. Goto, R. Granier de Cassagnac, N. Grau, S.V. Greene, M. Grosse Perdekamp, T. Gunji, T. Guo, H. Guragain, Y. Gu, J.S. Haggerty, K.I. Hahn, H. Hamagaki, J. Hanks, K. Hashimoto, R. Hayano, T.K. Hemmick, T. Hester, X. He, J.C. Hill, A. Hodges, R.S. Hollis, K. Homma, B. Hong, T. Hoshino, J. Huang, T. Ichihara, Y. Ikeda, K. Imai, Y. Imazu, M. Inaba, A. Iordanova, D. Isenhower, A. Isinhue, D. Ivanishchev, B.V. Jacak, S.J. Jeon, M. Jezghani, X. Jiang, Z. Ji, B.M. Johnson, K.S. Joo, D. Jouan, D.S. Jumper, J. Kamin, S. Kanda, B.H. Kang, J.H. Kang, J.S. Kang, J. Kapustinsky, G. Kasza, D. Kawall, A.V. Kazantsev, J.A. Key, V. Khachatryan, P.K. Khandai, A. Khanzadeev, K.M. Kijima, C. Kim, D.J. Kim, E.-J. Kim, Y.-J. Kim, Y.K. Kim, E. Kistenev, J. Klatsky, D. Kleinjan, P. Kline, T. Koblesky, M. Kofarago, B. Komkov, J. Koster, D. Kotchetkov, D. Kotov, L. Kovacs, F. Krizek, K. Kurita, M. Kurosawa, Y. Kwon, Y.S. Lai, J.G. Lajoie, A. Lebedev, D.M. Lee, G.H. Lee, J. Lee, K.B. Lee, K.S. Lee, S.H. Lee, M.J. Leitch, M. Leitgab, B. Lewis, X. Li, X. Li, S.H. Lim, M.X. Liu, D.A. Loomis, D. Lynch, S. Lökös, C.F. Maguire, Y.I. Makdisi, M. Makek, A. Manion, V.I. Manko, E. Mannel, M. McCumber, P.L. McGaughey, D. McGlinchey, C. McKinney, A. Meles, M. Mendoza, B. Meredith, Y. Miake, T. Mibe, A.C. Mignerey, A. Milov, D.K. Mishra, J.T. Mitchell, M. Mitrankova, Iu. Mitrankov, S. Miyasaka, S. Mizuno, A.K. Mohanty, S. Mohapatra, D.P. Morrison, M. Moskowitz, T.V. Moukhanova, B. Mulilo, T. Murakami, J. Murata, A. Mwai, T. Nagae, S. Nagamiya, J.L. Nagle, M.I. Nagy, I. Nakagawa, Y. Nakamiya, K.R. Nakamura, T. Nakamura, K. Nakano, C. Nattrass, P.K. Netrakanti, M. Nihashi, T. Niida, R. Nouicer, N. Novitzky, T. Novák, G. Nukazuka, A.S. Nyanin, E. O'Brien, C.A. Ogilvie, H. Oide, K. Okada, M. Orosz, A. Oskarsson, K. Ozawa, R. Pak, V. Pantuev, V. Papavassiliou, I.H. Park, J.S. Park, S. Park, S.K. Park, L. Patel, S.F. Pate, J.-C. Peng, D.V. Perepelitsa, G.D.N. Perera, D.Yu. Peressounko, J. Perry, R. Petti, C. Pinkenburg, R.P. Pisani, M. Potekhin, M.L. Purschke, H. Qu, J. Rak, I. Ravinovich, K.F. Read, D. Reynolds, V. Riabov, Y. Riabov, E. Richardson, D. Richford, N. Riveli, D. Roach, S.D. Rolnick, M. Rosati, M.S. Ryu, B. Sahlmueller, N. Saito, T. Sakaguchi, H. Sako, V. Samsonov, M. Sarsour, S. Sato, S. Sawada, K. Sedgwick, J. Seele, R. Seidl, Y. Sekiguchi, A. Seleznev, A. Sen, R. Seto, P. Sett, D. Sharma, A. Shaver, I. Shein, T.-A. Shibata, K. Shigaki, M. Shimomura, K. Shoji, P. Shukla, A. Sickles, C.L. Silva, D. Silvermyr, B.K. Singh, C.P. Singh, V. Singh, M. Skolnik, M. Slunečka, K.L. Smith, S. Solano, R.A. Soltz, W.E. Sondheim, S.P. Sorensen, I.V. Sourikova, P.W. Stankus, P. Steinberg, E. Stenlund, M. Stepanov, A. Ster, S.P. Stoll, M.R. Stone, T. Sugitate, A. Sukhanov, J. Sun, Z. Sun, A. Takahara, A. Taketani, Y. Tanaka, K. Tanida, M.J. Tannenbaum, S. Tarafdar, A. Taranenko, E. Tennant, A. Timilsina, T. Todoroki, M. Tomášek, H. Torii, R.S. Towell, I. Tserruya, B. Ujvari, H.W. van Hecke, M. Vargyas, E. Vazquez-Zambrano, A. Veicht, J. Velkovska, M. Virius, V. Vrba, E. Vznuzdaev, R. Vértesi, X.R. Wang, D. Watanabe, K. Watanabe, Y. Watanabe, Y.S. Watanabe, F. Wei, S. Whitaker, S. Wolin, C.L. Woody, M. Wysocki, B. Xia, Y.L. Yamaguchi, A. Yanovich, S. Yokkaichi, I. Yoon, I. Younus, Z. You, I.E. Yushmanov, W.A. Zajc, A. Zelenski, S. Zhou

Nuclear Experiment · Cross-listed from nucl-th

Effects of light-cluster degrees of freedom on collective flows in heavy-ion collisions at FOPI energies

Xin Li, Si-Pei Wang, Rui Wang et al. (+4 more)

Within a lattice Boltzmann-Uehling-Uhlenbeck transport model coupled to a kinetic approach for light-cluster formation, we investigate the impact of explicit light-cluster degrees of freedom on collective flows in Au+Au collisions at FOPI energies with beam energies $E_{\rm beam}$= $120$–$1500 A$ MeV by using a density-, momentum-, and isospin-dependent N$5$LO Skyrme pseudopotential. We first benchmark the kinetic approach by comparing the calculated light-cluster yields with FOPI data in central Au+Au collisions. We then analyze the collective flows of protons and light nuclei (deuterons, tritons, $^{3}\mathrm{He}$, and $^{4}\mathrm{He}$) in mid-central collisions. For protons, calculations with and without dynamical light-cluster degrees of freedom are compared to quantify the influence of dynamical cluster formation on proton directed ($v_1$), elliptic ($v_2$), triangular ($v_3$), and quadrangular ($v_4$) flows. We find that the dynamical light-cluster effect appreciably modifies proton $v_1$–$v_4$ flows at $E_{\rm beam}=120$–$150 A$ MeV, remains visible at $E_{\rm beam}=250$–$400 A$ MeV, and gradually weakens at $E_{\rm beam}\gtrsim 600 A$ MeV. For light nuclei, the kinetic approach captures the overall beam-energy dependence of the FOPI flow data, with better agreement for $E_{\rm beam}\geq 400 A$ MeV. We further examine the nucleon-number scaling of $v_2/A$ in both model calculations and experimental data, finding that the kinetic light-cluster formation approach qualitatively reproduces the observed scaling behavior. These results highlight the importance of a dynamical treatment of light-cluster formation for interpreting collective flows in heavy-ion collisions below about $600 A$ MeV, although the clustering effects on proton flows are minor at higher collision energies.
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All authors Xin Li, Si-Pei Wang, Rui Wang, Zhen Zhang, Jie Pu, Chun-Wang Ma, Lie-Wen Chen

Nuclear Experiment · Cross-listed from physics.plasm-ph

Mass Spectrometry Studies of Hydrogen Ions Energy Distributions in an ECR- based Large Volume Plasma Source

Bibekananda Naik, Ramesh Narayanan, Debaprasad Sahu et al. (+2 more)

Plasma is produced in a Large Volume Plasma Source (LVPS; dia. = 1 m, height = 1m) using CW microwaves (= 400 - 600 W, 2.45 GHz), in a compact ECR plasma source (CEPS) attached to LVPS, at hydrogen gas pressures = 1 - 3 mTorr. Plasma expands along the CEPS magnetic field into LVPS. A Hiden Analytical HPR 60 molecular beam mass spectrometer (MBMS) is used to measure the H^- ion energy distribution functions (IEDFs) in the downstream plasma. Previous plasma characterization studies in LVPS indicated favourable downstream plasma conditions for volume production of H^- ions. Measurements conducted with the MBMS probe aligned facing the plasma flow = 80 cm downstream, gave typical H^- count rates = 3 x 10^5 counts /s, at = 400 W, = 1 mTorr, along with a distinct high energy tail (<= 20 eV). These and other results are analyzed in detail. The positive ion spectrum showed the H_3^+ count to be consistently high in all cases (= 60-70 %); the counts for H_2^+ and H^+ were =30-35 % and a =few %. Combining the Langmuir probe (LP) and MBMS data it is possible to determine the approximate densities in front of the MBMS probe aperture. At = 500 W and = 2 mTorr, one finds: n_(H^+) = 9.6 x 10^9 cm^(-3), n_(H_2^+) = 1.7 x 10^10 cm^(-3) and n_(H_3^+) = 4.3 x 10^10 cm^(-3). The corresponding H^- density, = 80 cm downstream is n_(H^-) = 3.9 x 10^8 cm^(-3). Accounting for all H^- losses due to scattering and destruction, one finds the effective mean free path for H^- loss to be = 12.4 cm. Noting that H^- formation takes place about = 10 - 30 cm downstream of the source exit, the approximate average H^- density in the formation zone is determined as = 5.5 x 10^10 cm^(-3). This value is remarkably encouraging for H^- production in volume mode, considering the large chamber volume and area, as well as the very moderate power used for the experiments.
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All authors Bibekananda Naik, Ramesh Narayanan, Debaprasad Sahu, Mainak Bandyopadhyay, Ashish Ganguli

Nuclear Experiment

Charm-quark collectivity from small to large systems with ALICE

Marcello Di Costanzo

In these proceedings, the elliptic flow ($v_2$) measurement of prompt charm hadrons in lead-lead (Pb-Pb) and oxygen-oxygen (OO) collisions at $\sqrt{s_{\mathrm{NN}}} = 5.36$ TeV, using the data collected during LHC Run 3 by the ALICE detector, is presented. The analysis is performed at midrapidity ($|y| < 0.8$) and hadronic decay channels are used to reconstruct the signal candidates. The $v_2$ coefficient is measured via the Scalar Product (SP) technique. The $v_2$ of prompt D$^0$, D$^+$, D$_\text{s}^+$ mesons, and $\Lambda_{\text{c}}^+$ baryons in semicentral Pb-Pb collisions is reported. These results achieve unprecedented precision and low-$p_{\text{T}}$ reach for the D mesons and highlight the first observation of the splitting of baryon and meson elliptic flow at intermediate $p_{\text{T}}$ in the charm sector. The prompt D-meson $v_2$ is also measured in peripheral Pb-Pb collisions and central OO collisions, probing the degree of thermal equilibration reached by charm quarks propagating in progressively smaller quark-gluon plasma media.
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Nuclear Experiment · Cross-listed from nucl-th

Necessary and sufficient conditions of nonlinear causality in viscous anisotropic hydrodynamics

Kento Yoshida, Shujun Zhao and Tetsufumi Hirano

We derive the necessary and sufficient conditions for nonlinear causality in viscous anisotropic hydrodynamics (VAH) within the approximation that neglects small correction terms. Relativistic hydrodynamics provides a successful description of the space-time evolution of the matter produced in relativistic heavy-ion collisions, yet the earliest stage at which a hydrodynamic description becomes valid remains an open question. VAH has been proposed as an extension of conventional viscous hydrodynamics (VH) that can accommodate the large pressure anisotropies of the early-time dynamics. However, in such far-from-equilibrium regimes, the nonlinear causality of the theory is not guaranteed. By analyzing the characteristic velocities of the VAH equations of motion, we derive a set of inequalities that ensures causal signal propagation in all directions. The resulting conditions take a remarkably simple form and admit a clear physical interpretation in terms of the characteristic modes of the anisotropic medium. These results establish the regime of validity of VAH and provide a foundation for its application to the early-time dynamics of relativistic heavy-ion collisions.
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